Raman spectroscopic evidence of impurity-induced structural distortion in SmB6

Thi Huyen Nguyen, Thi Minh Hien Nguyen, Boyoun Kang, Beongki Cho, Mancheon Han, Hyoung Joon Choi, Mihye Kong, Yongjae Lee, In Sang Yang

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4 Citations (Scopus)

Abstract

Impurity-induced structural distortion in SmB6 is suggested by Raman spectroscopy study on impurity-controlled samples. Significant differences in the Raman spectra of single crystals SmB6(6N), synthesized with 99.9999%-pure boron, and SmB6(3N), synthesized with 99.9%-pure boron, are detected. While no noticeable differences are detected in the X-ray diffraction of SmB6(3N) and SmB6(6N), all the Raman phonon modes of the T2g, Eg, and A1g of SmB6(3N) are clearly broader and shift to higher wavenumbers than those of SmB6(6N), and the T2g and Eg modes of SmB6(3N) show doublet features. Based on the high-pressure Raman measurements and phonon calculation in uniaxial compression model, we argue that small amount of impurities in SmB6(3N) is enough to induce anisotropic distortion in the B6 octahedra, leading to peculiar behaviors in Raman spectrum of SmB6(3N). Our results may present a clue for understanding the current puzzles about SmB6 of various origins with different impurities.

Original languageEnglish
Pages (from-to)1661-1671
Number of pages11
JournalJournal of Raman Spectroscopy
Volume50
Issue number11
DOIs
Publication statusPublished - 2019 Nov 1

Bibliographical note

Funding Information:
I. S. Y. acknowledges the support by the National Research Foundation of Korea (NRF) grant funded by the Korean Ministry of Science and ICT (2017R1A2B2009309). B. Y. K. and B. K. C. acknowledges the support by the NRF of Korea (Grant NRF-2017R1A2B2008538). M. H. and H. J. C. acknowledge support from the NRF of Korea (Grant 2011-0018306). Computational resources were provided by KISTI Supercomputing Center (Project KSC-2016-C3-0006). Y.L. is grateful for the NRF-2018R1A3B1052042 grant from the Korean Ministry of Science and ICT. In summary, microscopic changes in the structure of impurity-controlled SmB6 were investigated using Raman spectroscopy and first-principles calculations. The Raman spectra of SmB6(3N) and SmB6(6N) exhibited significant differences in wavenumber and line shape in contrast to essentially identical behavior in XRD patterns. We suggest that the presence of ~0.1% (at most) of impurities in SmB6(3N) induces a slight B6 octahedra distortion, such as spontaneous tilting away from the [001] direction, leading to significant upshifts of the phonon peak wavenumbers and broadening of the phonon modes of SmB6(3N) in comparison with those of SmB6(6N), the purest sample. The impurity-induced structural distortion in SmB6(3N) could be a common effect in RB6 including CaB6 and EuB6, leading to varieties of physical properties. This work exemplifies the strength of Raman spectroscopy to study the change in the microscopic structure of materials composed of light element such as RB6. I. S. Y. acknowledges the support by the National Research Foundation of Korea (NRF) grant funded by the Korean Ministry of Science and ICT (2017R1A2B2009309). B. Y. K. and B. K. C. acknowledges the support by the NRF of Korea (Grant NRF-2017R1A2B2008538). M. H. and H. J. C. acknowledge support from the NRF of Korea (Grant 2011-0018306). Computational resources were provided by KISTI Supercomputing Center (Project KSC-2016-C3-0006). Y.L. is grateful for the NRF-2018R1A3B1052042 grant from the Korean Ministry of Science and ICT.

Funding Information:
I. S. Y. acknowledges the support by the National Research Foundation of Korea (NRF) grant funded by the Korean Ministry of Science and ICT (2017R1A2B2009309). B. Y. K. and B. K. C. acknowledges the support by the NRF of Korea (Grant NRF‐2017R1A2B2008538). M. H. and H. J. C. acknowledge support from the NRF of Korea (Grant 2011‐0018306). Computational resources were provided by KISTI Supercomputing Center (Project KSC‐2016‐C3‐0006). Y.L. is grateful for the NRF‐2018R1A3B1052042 grant from the Korean Ministry of Science and ICT.

Publisher Copyright:
© 2019 The Authors. Journal of Raman Spectroscopy published by John Wiley & Sons Ltd

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Spectroscopy

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